1. Field of the Invention
The present invention relates to wastewater treatment, and particularly to a system that removes oil, sludge, organic contaminants and bacteria from wastewater generated in homes or buildings that do not have access to a public sewer system so that the treated wastewater can be used for watering lawns or recharging groundwater, or for pretreatment of water discharged into the public sewer system.
2. Description of the Related Art
In order to protect the environment and promote public health, communities typically require wastewater treatment. The discharge of untreated wastewater is not suitable, since it gives rise to numerous environmental concerns. Untreated wastewater contains bacteria that consume high quantities of dissolved oxygen, which is commonly measured as the level of biochemical oxygen demand (BOD) in the water. Thus, when untreated wastewater is released into either aboveground or belowground streams and aquifers, the level of dissolved oxygen in the water of the streams and aquifers begins to deplete, which endangers the water bodies themselves and the resident plant and aquatic life. Over time, the bacteria of the untreated wastewater will deplete the dissolved oxygen in the water to a level that will not support plant and aquatic life. Additionally, in developing nations, where potable water is scarce, it is often desirable to recover as much potable water as possible from wastewater, rather than disposing of both the potable water and the contaminants.
To treat wastewater, communities in highly populated areas commonly collect wastewater and transport it through a series of underground pipes to a centralized wastewater treatment plant. However, there are several problems associated with centralized treatment plants. Centralized wastewater treatment plants are designed and rated for processing a specific flow rate of wastewater per day, typically expressed as the rated capacity of the plant, and all treatment plants have a maximum flow rate capacity. Thus, if a centralized treatment plant receives more wastewater on a particular day than what the plant was designed to handle, problems are encountered. For example, when a treatment plant receives larger-than-normal amounts of untreated raw wastewater, a portion of the untreated wastewater must be diverted into a body of water, such as a river, in order not to exceed the amount of wastewater the plant was designed to handle.
As noted above, discharge of this untreated wastewater into bodies of water will eventually endanger and kill resident plant and aquatic life in the water. Untreated wastewater also contains a number of disease pathogens that are extremely harmful to humans. For example, untreated wastewater is one of the leading causes of dysentery, which can be life threatening if not properly treated. Thus, if a significant amount of untreated wastewater is discharged into a body of water, that body of water will become unavailable for human consumption. On the other hand, if the treatment plant processes the larger-than-normal amounts of untreated wastewater, instead of diverting a portion into a body of water, the influx of untreated wastewater would wash away the bacteria populations used by the plant to treat the untreated wastewater, which would disrupt the entire biological treatment process of the plant. Further, as noted above, wastewater treatment is particularly needed in developing nations, and such large-scale treatment plants may not be available.
In rural areas and in developing nations, construction of centralized wastewater treatment plants may be too expensive to build and maintain. In addition, the cost of connecting residences and businesses in rural areas to a centralized treatment plant via sewage lines may be impracticable due to the greater distance between the those residences and businesses. In such areas, septic systems are usually utilized to treat wastewater. A septic tank is typically a large tank located underground on an owner's property. Septic tanks are categorized as continuous flow systems because wastewater flows into the septic tank at one end, and the same amount of wastewater that entered will exit the tank at the other end. The purpose of a septic tank is to retain any solids in the wastewater and to allow the liquid wastewater to pass through to prevent field lines leading from the septic tank to a drain field from becoming clogged. However, since the wastewater leaving the septic tank has not been treated, the wastewater will be a detriment to the environment, as noted above, and may not be recovered as potable water. Furthermore, as solids build up inside the septic tank, a phenomenon known as periodic upset may occur, causing solids to flow out of the septic tank and into the field lines connected to the tank. Eventually, these field lines will clog due to the buildup and carryover of solids. When this occurs, the field lines have to be excavated and cleaned, which means destruction to a portion of the owner's property as well as increased expense to the owner. Thus, a wastewater treatment system solving the aforementioned problems is desired.